Technology for creating images accompanied by depth information by acquiring the distance (depth or z-distance) between a photographed object and a camera has been known from before. Such images are often called 2.5-dimensional images (for example, see Non Patent Literature 1).
On the other hand, technology has been proposed for separating regions where virtually static backgrounds are depicted and regions where moving objects are depicted, from moving images depicting states in which an object's position, shape, color and/or the like change (for example, see Patent Literature 1).
By combining such technologies, it is possible to generate 2.5-dimensional moving images in which background depth and object depth are distinguished, after separating the background and the objects moving in the front thereof. In frames comprising the 2.5-dimensional images, the object's surface (object's front surface) as seen from the camera is depicted, and in pixels included in the depiction region where the object is depicted, the color of the surface part of the object corresponding to those pixels, along with the depth to that surface part (anterior-surface depth), are associated.
This kind of 2.5-dimensional moving image can be obtained using detection by a depth sensor simultaneously with shooting of the real world by a CCD camera, or shooting the real world with a stereo camera for stereopsis, finding parallax for each corresponding pixel and calculating depth from that parallax. Here, in a 2.5-dimensional moving image made by shooting the real world, the state of the object's surface (object's rear surface) that is not depicted in the frame is not photographed, and information about the depth to the rear surface is not known.
In addition, after creating a moving image expressing a state taking into consideration and causing movement and/or the like of an object in a virtual space, by adding only the anterior-surface depth in each pixel of the moving image, it is possible to obtain a 2.5-dimensional moving image. That this kind of transformation is accomplished is convenient for reasons such as consistency of the format and the 2.5-dimensional moving image being maintained and video editing becoming easier.
In the field of three-dimensional graphics, clash determination technology is widely used in order to prevent regions occupied by objects from mutually encroaching on each other so that objects moving in virtual space do not interfere, and to prevent situations in which one penetrates the other. Clash as referred to here naturally includes surface contact among objects, and also includes cases in which regions mutually occupied overlap and cases in which the distance between two objects is closer than a given threshold value even though the two are actually separated, thus having a broader meaning than the everyday definition.